The synthetic double-stranded RNA, polyriboinosinic-polyribocytidylic acid (poly I:C), is effective as an interferon inducer in rodents and rabbits and as such provides protection against a variety of RNA and DNA viruses in these species [A. K. Field et al., Proc. Natl. Acad. Sci. U.S.A., 58, pp. 1004-1010, (1967)]. However, poly I:C shows only a very weak capacity to induce interferon in man and non-human primates.
It has been stated that enzymatic inactivation of poly I:C is the reason for its poor capacity to induce interferon in primates [H. B. Levy et al., J. Inf. Dis., 132, p. 434 (1975)]. These authors have reported the preparation of a solubilized formulation of poly I:C and poly-L-lysine (molecular weight 2000 to 5000) in carboxymethylcellulose (CMC) as the solubilizing agent [see also Levy, U.S. Pat. No. 3,952,097 (1976)]. This complex is relatively resistant to ribonuclease and induces significant quantities of interferon in rhesus monkeys, chimpanzees and man.
However, certain disadvantages are associated with CMC. It is a polysaccharide which is at best poorly biodegradable and on repeated injection may cause deposition of residues which may cause irritations (pathology). In addition, CMC has been considered to be a potential carcinogen. Both the sodium and ammonium salts of CMC appear on the NIOSH Suspected Carbinogen List, U.S. Environmental Protection Agency, Office of Toxic Substances, March, 1976. The references upon which these listings were made are: A. L. Walpole, Morphol. Precursors Cancer, Proc. Inter. Conf. Perugia, Italy, pp. 83-88, 1961 (Publ. 1962) and Rev. Canad. Biol. (Mont.), 20, pp. 701 (1961).